Method and system for large scale manufacture of thin film photovoltaic devices using single-chamber configuration

ABSTRACT

A system for large scale manufacture of thin film photovoltaic cells includes a chamber comprising a plurality of compartments in a common vacuum ambient therein. Additionally, the system includes one or more shutter screens removably separating each of the plurality of compartments. The system further includes one or more transfer tools configured to transfer a substrate from one compartment to another without breaking the common vacuum ambient. The substrate is optically transparent and is characterized by a lateral dimension of about 1 meter or greater for a solar module. Embodiments of the invention provide compartments configured to subject the substrate to one or more thin film processes to form a Cu-rich Cu—In composite material overlying the substrate and at least one of the plurality of compartments is configured to subject the Cu-rich Cu—In composite material to a thermal process to form a chalcogenide structured material.

This application is a continuation of U.S. patent application Ser. No.12/269,774 filed on Nov. 12, 2008, which claims priority to U.S.Provisional Application No. 60/988,089 filed Nov. 14, 2007 and U.S.Provisional Patent Application No. 60/988,099, filed Nov. 14, 2007,commonly assigned and incorporated by references herein for allpurposes. This application is also related to U.S. patent applicationSer. No. 11/748,444, filed May 14, 2007 and U.S. patent application Ser.No. 11/804,019, filed May 15, 2007, both of which are commonly assignedand incorporated by references herein for all purposes.

BACKGROUND OF THE INVENTION

The present invention relates generally to photovoltaic materials. Moreparticularly, the present invention provides a method and system forlarge scale manufacture of multi-junction and single-junction solarcells using integrated manufacturing systems for thin and thick filmphotovoltaic materials. Merely by way of example, the present method andstructure have been implemented using a solar module having multiplethin film materials, but it would be recognized that the invention mayhave other configurations.

From the beginning of time, human beings have been challenged to findway of harnessing energy. Energy comes in the forms such aspetrochemical, hydroelectric, nuclear, wind, biomass, solar, and moreprimitive forms such as wood and coal. Over the past century, moderncivilization has relied upon petrochemical energy as an importantsource. Petrochemical energy includes gas and oil. Gas includes lighterforms such as butane and propane, commonly used to heat homes and serveas fuel for cooking. Gas also includes gasoline, diesel, and jet fuel,commonly used for transportation purposes. Heavier forms ofpetrochemicals can also be used to heat homes in some places.Unfortunately, petrochemical energy is limited and essentially fixedbased upon the amount available on the planet Earth. Additionally, asmore human beings begin to drive and use petrochemicals, it is becominga rather scarce resource, which will eventually run out over time.

More recently, clean sources of energy have been desired. An example ofa clean source of energy is hydroelectric power. Hydroelectric power isderived from electric generators driven by the force of water that hasbeen held back by large dams such as the Hoover Dam in Nevada. Theelectric power generated is used to power up a large portion of LosAngeles Calif. Other types of clean energy include solar energy.Specific details of solar energy can be found throughout the presentbackground and more particularly below.

Solar energy generally converts electromagnetic radiation from our sunto other useful forms of energy. These other forms of energy includethermal energy and electrical power. For electrical power applications,solar cells are often used. Although solar energy is clean and has beensuccessful to a point, there are still many limitations before itbecomes widely used throughout the world. As an example, one type ofsolar cell uses crystalline materials, which form from semiconductormaterial ingots. These crystalline materials include photo-diode devicesthat convert electromagnetic radiation into electrical current.Crystalline materials are often costly and difficult to make on a widescale. Additionally, devices made from such crystalline materials havelow energy conversion efficiencies. Other types of solar cells use “thinfilm” technology to form a thin film of photosensitive material to beused to convert electromagnetic radiation into electrical current.Similar limitations exist with the use of thin film technology in makingsolar cells. That is, efficiencies are often poor. Additionally, filmreliability is often poor and cannot be used for extensive periods oftime in conventional environmental applications. There have beenattempts to form heterojunction cells using a stacked configuration.Although somewhat successful, it is often difficult to match currentsbetween upper and lower solar cells. These and other limitations ofthese conventional technologies can be found throughout the presentspecification and more particularly below.

From the above, it is seen that improved techniques for manufacturingphotovoltaic materials and resulting devices are desired.

BRIEF SUMMARY OF THE INVENTION

The present invention relates generally to photovoltaic materials. Moreparticularly, the present invention provides a method and system forlarge scale manufacture of multi-junction and single-junction solar cellusing integrated manufacturing system and method for thin and thick filmphotovoltaic materials. Merely by way of example, the present method andstructure have been implemented using a solar module having multiplethin film materials, but it would be recognized that the invention mayhave other configurations.

According to a specific embodiment, the invention provides system formanufacturing a photovoltaic device. The system includes a first loadlock station and a second load lock station. The system also includes aplurality of process stations arranged in a serial configuration betweenthe first and the second load lock stations. The plurality of processstations numbered from 1 through N, where N is an integer greater than2. In a specific embodiment, the system includes a transfer stationcoupled between two adjacent process stations.

According to another embodiment, the invention provides a system formanufacturing a photovoltaic device. The system includes a load lockstation and a plurality of process station. Each of the plurality ofprocess stations being coupled to the load lock station. In a specificembodiment, the system also includes a transport station coupled betweena first process station and the load lock station.

According to other embodiments of the invention, various methods areprovided for large scale manufacture of photovoltaic devices. In aspecific embodiment, the method includes loading a substrate into a loadlock station and transferring the substrate in a controlled ambient to afirst process station. The method includes using a first physicaldeposition process in the first process station to cause formation of afirst conductor layer overlying the surface region of the substrate. Themethod includes transferring the substrate to a second process station,and using a second physical deposition process in the second processstation to cause formation of a second layer overlying the surfaceregion of the substrate. The method further includes repeating thetransferring and processing until all thin film materials of thephotovoltaic devices are formed.

In another embodiment, the invention also provides a method for largescale manufacture of photovoltaic devices including feed forwardcontrol. That is, the method includes in-situ monitoring of thephysical, electrical, and optical properties of the thin films. Theseproperties are used to determine or adjust process conditions forsubsequent processes.

In an alternative embodiment, the present invention provides a systemfor large scale manufacture of thin film photovoltaic cells. The systemincludes a chamber comprising a plurality of compartments in a commonvacuum ambient therein. The system further includes one or more shutterscreens removably separating each of the plurality of compartments andone or more transfer tools configured to transfer a substrate from onecompartment to another without breaking the common vacuum ambient. Thesubstrate is optically transparent and is characterized by a lateraldimension of about 1 meter or greater for a solar module. Embodiments ofthe invention provide that at least some of the plurality ofcompartments are configured to subject the substrate to one or more thinfilm processes to form a Cu-rich Cu—In composite material overlying thesubstrate and at least one of the plurality of compartments isconfigured to subject the Cu-rich Cu—In composite material to a thermalprocess to form a chalcogenide structured material.

In yet another embodiment, the present invention provides a method formanufacture of thin film photovoltaic cells in a system withsingle-chamber configuration. The method includes providing a substrateinto a chamber. The substrate is optically transparent and ischaracterized by a lateral dimension of about 1 meter or greater formanufacture a thin film photovoltaic cell. The method further includesforming an electrode layer overlying the substrate and transferring thesubstrate within the chamber to subject the electrode layer to a copperbearing sputtering target. Additionally, the method includes forming acopper-bearing layer overlying the electrode layer and transferring thesubstrate within the chamber to subject the copper-bearing layer to anindium sputtering target. The method further includes forming an indiumlayer overlying the copper-bearing layer which correspondingly leads toa formation of a Cu-rich Cu—In composite film having a Cu:In atomicratio of 1.2:1 and greater. Furthermore, the method includestransferring the substrate to a compartment within the chamber. Thecompartment comprises a plurality of nozzles for supplying gas phasesulfur-bearing species and one or more heaters for supply thermalenergy. Moreover, the method includes performing a thermal treatmentprocess to form a photovoltaic absorber layer by reacting the Cu-richCu—In composite film with the sulfur-bearing species.

Various additional objects, features and advantages of the presentinvention can be more fully appreciated with reference to the detaileddescription and accompanying drawings that follow.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a simplified view diagram of a system for large scalemanufacture of thin film photovoltaic devices according to an embodimentof the present invention;

FIG. 1B is a simplified view diagram of a system for large scalemanufacture of thin film photovoltaic devices according to analternative embodiment of the present invention;

FIG. 2 is a simplified view diagram of a control system for the systemfor large scale manufacture of thin film photovoltaic devices of FIG. 1according to an embodiment of the present invention;

FIG. 3 is a simplified view diagram of a single physical vapordeposition tool which can be part of a system for large scalemanufacture of thin film photovoltaic devices according to anotherembodiment of the present invention;

FIG. 4 is a simplified flow chart illustrating a method for large scalemanufacture of thin film photovoltaic devices according to an embodimentof the present invention;

FIG. 5 is a simplified flow chart illustrating a method for large scalemanufacture of thin film photovoltaic devices according to anotherembodiment of the present invention;

FIGS. 6-8 are simplified flow charts illustrating a method for largescale manufacture of thin film photovoltaic devices according to anotherembodiment of the present invention;

FIG. 9 is a simplified flow chart illustrating a method for large scalemanufacture of thin film photovoltaic devices according to anotherembodiment of the present invention;

FIG. 10 is a simplified flow chart illustrating a method for large scalemanufacture of thin film photovoltaic devices according to anotherembodiment of the present invention;

FIG. 11 is a simplified flow chart illustrating a method for large scalemanufacture of thin film photovoltaic devices according to an embodimentof the present invention;

FIG. 12 is a simplified flow chart illustrating a method for large scalemanufacture of thin film photovoltaic devices according to anotherembodiment of the present invention;

FIG. 13 is a simplified schematic diagram showing a system withsingle-chamber configuration for large scale manufacture of thin filmphotovoltaic cells according to an embodiment of the present invention;

FIGS. 14-16 are simplified schematic diagrams showing additionalprocesses of a method for large scale manufacture of thin filmphotovoltaic cells using single-chamber configuration according to anembodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

The present invention relates generally to photovoltaic materials. Moreparticularly, the present invention provides a method and system forlarge scale manufacture of multi-junction and single-junction solarcells using integrated manufacturing systems for thin and thick filmphotovoltaic materials. Merely by way of example, the present method andstructure have been implemented using a solar module having multiplethin film materials, but it would be recognized that the invention mayhave other configurations.

FIG. 1A is a simplified view diagram of a system 100 for large scalemanufacture of thin film photovoltaic devices according to an embodimentof the present invention. This diagram is merely an example, whichshould not unduly limit the scope of the claims herein. One of ordinaryskill in the art would recognize other variations, modifications, andalternatives. As shown, system 100 includes load locks #1 and #2 forproviding an interface between system 100 and the environment. System100 also includes process stations P1, P2, . . . , Pm, and transportstations T1, T2, T3, . . . , Tn. Each process station is configured toperform a process required to form the thin film photovoltaic device.Depending on the embodiment, the processes can include thin filmformation, patterning, etching, annealing, etc. The process stations arecapable of supplying process gases, maintaining process temperature,maintaining process pressure, etc.

In a specific embodiment, a substrate, e.g. a glass substrate, isentered into system 100 through lord lock #1, which can be pumped downto a reduced pressure. In an implementation, transport stations T1-Tnare configured to allow the substrate to be transported between a loadlock and a process station, or between two process stations. Thetransport stations can provide a controlled ambient to maintaincleanliness of the substrate. For example, a transport station can allowa substrate to be transferred in a vacuum. In another example, atransport station may provide an inert gas ambient of, e.g. nitrogen orargon, and can be maintained at atmospheric pressure or at a reducedpressure. In another implementation, transport stations T1-Tn areconfigured to serve a temporary dividers between the process stationsP1-Pn that essentially are separate compartments belonging to asingle-chamber configured system. In particular, some transport stationsof T1-Tn may be able to seal vacuum and have thermal isolation functionso that a process station or compartment can temporarily have differentpressure and temperature ambient compared to its neighboring processstation or compartment.

FIG. 1B is a simplified view diagram of a system 150 for large scalemanufacture of thin film photovoltaic devices according to analternative embodiment of the present invention. This diagram is merelyan example, which should not unduly limit the scope of the claimsherein. One of ordinary skill in the art would recognize othervariations, modifications, and alternatives. As shown, system 150includes a load lock, multiple process stations, and multiple transportstations. The functions of the load lock, process stations, andtransport stations are similar to those discussed above in connectionwith system 100 in FIG. 1. System 150, however, has a differentconfiguration. A central load lock is connected to transport stationsT1, T2, . . . , Tn, which in turn are coupled to process stations P1,P2, . . . , Pn. In a specific embodiment, after each process steps, thesubstrate is returned to the central load lock, and the next processstation is selected for the next process. Of course, one of ordinaryskilled in the art can recognize other configurations, variations,modifications. For example, system 150 can be reconfigured to be asingle-chamber system. Within the single-chamber configuration, the loadlock is just one compartment of the single-chamber configuration.Additionally, each of the process stations can be a independentcompartment of the single-chamber configuration that can have a sharedvacuum conditions controlled by one or more commonly coupled pumps.Transport stations serve as a temporary divider between each pair ofcompartments. In particular, one or more transport stations can bevacuum sealer and thermal isolator for a particular process station orcompartment to perform certain thin film process at different vacuumcondition or at different temperature ambient.

System 100 and system 150 are examples of systems for large scalemanufacture of thin film photovoltaic devices according to embodimentsof the present invention. Depending on the embodiment, the system isconfigured to allow formation of junction between the window layer andthe absorber layer without breaking vacuum and to keep moisture,particles, and oxygen from contaminating the substrate and the deviceduring process. In a specific example, load locks and transport stationsare provided. Inert gases can also be used at reduced or atmosphericpressure.

In a specific embodiment, a process sequence in system 100 for largescale manufacture of photovoltaic devices can be briefly summarizedbelow.

-   -   1. Load substrate into the load-lock;    -   2. Pump down the load lock, turn on the heater, and flow inert        gas (Ar or N₂) until substrate reaches set temperature;    -   3. Transfer substrate into the selected process station chamber;    -   4. Flow process gas, turn on sputtering power, and start the        sputtering process;    -   5. Once process is finished, select the next station (process or        transfer station), transfer the substrate;    -   6. Perform the next process in the next process station; and    -   7. After the process is completed, the substrate is transferred        to the second load-lock. The second load lock is vented, and the        substrate is removed from the system.

FIG. 2 is a simplified view diagram of a control system 200 for thesystem for large scale manufacture of thin film photovoltaic devices ofFIG. 1 according to an embodiment of the present invention. This diagramis merely an example, which should not unduly limit the scope of theclaims herein. One of ordinary skill in the art would recognize othervariations, modifications, and alternatives. As shown, control system200 includes processors, memories, user interface devices, and interfaceto network. In an embodiment, the control system performs variouscontrol functions of, for example, system 100 or system 150.

In a specific embodiment, the control system 200 also controls variousdiagnostic tools disposed in-situ in systems 100 and 150 for criticalprocess steps, such as formation of absorber layer and the window layer.Thin film properties are monitored in-situ. Electrical and opticalproperties are also measured in-situ in the process station. Theelectrical properties are measured either using probes or using acontactless method. The electrical properties are also used to detectshunts in the thin films. The data is used in feedback to adjust secondprocess for absorber layer or window layer. Alternatively, thediagnostic and monitoring tools can also be used in a feed forwardprocess for adjusting the next process for a second cell or within thecell design. In an embodiment, a process can be stopped based on in-situmeasurement data. In another embodiment, process parameters are adjustedbefore the process is resumed.

FIG. 3 is a simplified view diagram of a single physical vapordeposition (PVD) tool which can be part of a system for large scalemanufacture of thin film photovoltaic devices according to anotherembodiment of the present invention. This diagram is merely an example,which should not unduly limit the scope of the claims herein. One ofordinary skill in the art would recognize other variations,modifications, and alternatives. A PVD process is often carried out bysputtering in which collision of high-energy particles with sputteringtargets to deposit materials ejected from the sputtering targets on asubstrate. In a sputtering process thin films can be formed to a uniformthickness over a large area, and the composition ratio of thin films canbe easily adjusted. In magnetron sputtering a magnetic field is used tohelp create a high-density plasma of energetic particles in a reactionchamber, usually under a low pressure.

As shown in FIG. 3, a substrate 31 is disposed in a vacuum chamber 32. Atarget 34 is disposed on the opposite side from the substrate 32.Magnets 35 are disposed behind the target 34 to form magnetic fieldlines of predetermined directions. In addition, a power supply unit 37supplies a voltage to an electrode 38 which is coupled to target 34.During processing, a vacuum is maintained in the chamber, a gas such asargon is introduced in the chamber, and electric discharge createsplasma. Energetic particles collide with the target and cause atoms tobe ejected from the target and deposited on the substrate to form a thinfilm.

One or more process stations in system 100 in FIG. 1A or system 150 inFIG. 1B may include a balanced magnetron sputtering station. In aspecific embodiment, the magnet field are arranged to focus the plasmafor large areas of substrate and to provide a uniform thin film over alarge area. Depending on the embodiment, the size of the substrate canbe 2′ by 5′ or larger. In an embodiment, when the sputtering targets canbe about five foot wide or even wider, scanning magnetrons is used tokeep uniformity of films. In an embodiment, the sputtering stationsallow formation of thin films over large areas substantially free ofpin-holes.

According to embodiments of the present invention, various methods areprovided for large scale manufacture of photovoltaic devices. Examplesof these methods are discussed below in connection with the drawingsprovided in FIGS. 4-12. It is noted that, in the examples discussedbelow, transferring the substrate in a controlled ambient can be carriedout in different way. For example, the substrate can be transferredunder reduced pressure, or the substrate can be transferred in anambient of an inert gas, such as N₂ and Ar. Alternatively, the transfercan be carried out under atmospheric pressure in an inert gas.Additionally, physical deposition processes are used extensively in theexamples discussed below. It is noted that in a specific embodiment, thephysical deposition processes include sputtering using balancedmagnetron.

In various embodiments discussed below, the substrate is asemiconductor, for example, silicon, germanium, compound semiconductormaterial such as a III-V gallium arsenide, germanium, silicon germanium,and others. Alternatively, the substrate can be a transparent substratesuch as glass, quartz, fused silica, and others. Other examples of thesubstrate include a polymer material or a metal material. The metalchalcogenide material in the examples discussed below include copper(II) oxide (CuO) having a bandgap of about 1.2 eV and others. In aspecific embodiment, the first bandgap is less than the second bandgap.

The conductor layers used in various embodiments can be aluminum,tungsten, or other metallic material. The conductor layer can also be atransparent conducting oxide material such as ZnO:Al, SnO:F, ITO, orothers. The conductor layer can also be a conductive polymer material.Examples of various materials used in photovoltaic devices can be foundin U.S. patent application Ser. No. 11/748,444, filed May 14, 2007, U.S.patent application Ser. No. 11/804,019, filed May 15, 2007, andconcurrently filed U.S. Provisional Patent Application No. 60/988,099,filed Nov. 14, 2007. All these applications are commonly assigned, andtheir contents are hereby incorporated by reference for all purposes.

FIG. 4 is a simplified flow chart illustrating a method for large scalemanufacture of single-junction thin film photovoltaic devices accordingto an embodiment of the present invention. This diagram is merely anexample, which should not unduly limit the scope of the claims herein.One of ordinary skill in the art would recognize other variations,modifications, and alternatives. As shown, the method of manufacturing asingle-junction photovoltaic device, also known as the substrate method,can be summarized as follows.

-   -   1. loading a substrate into a load lock station, the substrate        including a surface region;    -   2. transferring the substrate under a controlled ambient to a        first process station;    -   3. using a first physical deposition process in the first        process station to cause formation of a first conductor layer        overlying the surface region of the substrate;    -   4. transferring the substrate under reduced pressure to a second        process station;    -   5. using a second physical deposition process in the second        process station to cause formation of a first p-type absorber        material, the first p-type absorber material comprising at least        a first metal chalcogenide material overlying the first        conductor layer, the first p-type absorber material being        characterized by a first bandgap range and a first thickness        range;    -   6. monitoring properties of the first p-type absorber material        in the second process station;    -   7. transferring the substrate in a controlled ambient to a third        process station;    -   8. using a third physical deposition process in the third        process station to cause formation of a first n-type window        layer, the first n-type window layer comprising at least a        second metal chalcogenide material overlying the first p-type        absorber layer; In a specific embodiment, the third physical        deposition process is determined based on the properties of the        first p-type absorber material;    -   9. transferring the substrate under a controlled ambient to a        fourth process station; and    -   10. using a fourth physical deposition process in the fourth        process station to cause formation of a second conductor layer        overlying the second buffer layer.

In a specific embodiment, the method also includes forming a secondbarrier layer overlying the first conductor layer. In anotherembodiment, the method includes forming a first high resistivity layeroverlying the first conductor layer before the formation of the firstp-type absorber material, the first buffer layer being characterized bya resistivity greater than about 10 kohm-cm. The buffer layer issometimes referred to as a high-resistance transparent conducting oxidebuffer layers or HRT. The HRT can minimize effect of shunt defects. In aspecific embodiment, the resistivity HRT is about 10 kohm percentimeter, whereas the resistivity of the transparent conduction oxidelayer (TCO) is about 7 to 10 ohms per centimeter. In another specificembodiment, the method further includes in-situ monitoring properties ofthe layer being formed in each process station and determining a processcondition in a subsequent physical deposition process based on dataobtained in the monitoring of the earlier processes.

FIG. 5 is a simplified flow chart illustrating a method for large scalemanufacture of thin film photovoltaic devices according to anotherembodiment of the present invention. This diagram is merely an example,which should not unduly limit the scope of the claims herein. One ofordinary skill in the art would recognize other variations,modifications, and alternatives. As shown, another method ofmanufacturing a single-junction photovoltaic device, also known as thesuperstrate method, can be briefly summarized below.

-   -   1. loading a substrate into a load lock station, the substrate        including a surface region;    -   2. transferring the substrate under a controlled ambient to a        first process station;    -   3. using a first physical deposition process in the first        process station to cause formation of a first conductor layer        overlying the surface region of the substrate;    -   4. transferring the substrate under reduced pressure to a second        process station;    -   5. using a second physical deposition process in the second        process station to cause formation of a first n-type window        layer, the first n-type window layer comprising at least a        second metal chalcogenide material overlying the first p-type        absorber layer;    -   6. monitoring properties of the first n-type window layer in the        second process station;    -   7. transferring the substrate in a controlled ambient to a third        process station;    -   8. using a third physical deposition process in the third        process station to cause formation of a first p-type absorber        material, the first p-type absorber material comprising at least        a first metal chalcogenide material overlying the first        conductor layer, the first p-type absorber material being        characterized by a first bandgap range and a first thickness        range; in a specific embodiment, the third physical deposition        process is determined based on the properties of the first        n-window layer;    -   9. transferring the substrate under a controlled ambient to a        fourth process station; and    -   10. using a fourth physical deposition process in the fourth        process station to cause formation of a second conductor layer        overlying the second buffer layer.

In a specific embodiment, the method of FIG. 5 also includes a feedforward control. The method includes the additional processes of in-situmonitoring properties of the layer being formed in each process station,and determining a process condition in a subsequent physical depositionprocess based on data obtained in the monitoring of the earlierprocesses.

FIGS. 6-8 are simplified flow charts illustrating a method for largescale manufacture of thin film photovoltaic devices according to anotherembodiment of the present invention. This diagram is merely an example,which should not unduly limit the scope of the claims herein. One ofordinary skill in the art would recognize other variations,modifications, and alternatives. As shown, the method is for making twophotovoltaic devices stacked to make a tandem device, with eachphotovoltaic device having two terminals. The method can be brieflysummarized as follows.

-   -   1. forming a top photovoltaic device using the superstrate        method of FIG. 5 as described above;    -   2. forming a bottom photovoltaic device using the substrate        method of FIG. 4 as described above;    -   3. forming an insulator layer overlying the bottom photovoltaic        device; and    -   4. mounting the top photovoltaic device over the insulator layer        and the bottom photovoltaic device.        In a specific embodiment, the top device, the insulator layer,        and the bottom layer are laminated together with an EVA        material. Of course, other kinds of adhesive materials can also        be used. In another specific embodiment, the method further        includes a feed forward process which allows monitoring device        properties of the top photovoltaic device and adjusting device        parameters and process conditions for the bottom photovoltaic        device.

FIG. 9 is a simplified flow chart illustrating a method for large scalemanufacture of thin film photovoltaic devices according to anotherembodiment of the present invention. This diagram is merely an example,which should not unduly limit the scope of the claims herein. One ofordinary skill in the art would recognize other variations,modifications, and alternatives. As shown, the method is formanufacturing a tandem photovoltaic device, which includes twophotovoltaic junctions but has only two external terminals. The methodcan be briefly summarized as follows.

-   -   1. loading a substrate into a load lock station, the substrate        including a surface region;    -   2. transferring the substrate in a controlled ambient to a first        process station;    -   3. using a first physical deposition process in the first        process station to cause formation of a first conductor layer        overlying the surface region of the substrate;    -   4. transferring the substrate in a controlled ambient to a        second process station;    -   5. using a second physical deposition process in the second        process station to cause formation of a first p-type absorber        material, the first p-type absorber material comprising at least        a first metal chalcogenide material overlying the first        conductor layer, the first p-type absorber material being        characterized by a first bandgap range and a first thickness        range;    -   6. transferring the substrate in a controlled ambient to a third        process station;    -   7. using a third physical deposition process in the third        process station to cause formation of a first n-type window        layer, the first n-type window layer comprising at least a        second metal chalcogenide material overlying the first p-type        absorber layer;    -   8. transferring the substrate in a controlled ambient to a        fourth process station;    -   9. using a fourth physical deposition process in the fourth        process station to cause formation of an n++ type semiconductor        material;    -   10. transferring the substrate in a controlled ambient to a        fifth process station;    -   11. using a fifth physical deposition process in the fifth        process station to cause formation of an p++ type semiconductor        material, the p++ semiconductor material and the n++        semiconductor material forming a tunneling junction layer;    -   12. transferring the substrate in a controlled ambient to a        sixth process station;    -   13. using a sixth physical deposition process in the sixth        process station to cause formation of a second p-type absorber        material, the second p-type absorber material comprising at        least a third metal chalcogenide material overlying the        tunneling junction layer, the second p-type absorber material        being characterized by a second bandgap range and a second        thickness range;    -   14. transferring the substrate in a controlled ambient to a        seventh process station;    -   15. using a seventh physical deposition process in the seventh        process station to cause formation of a second n-type window        layer, the second n-type window layer comprising at least a        fourth metal chalcogenide material overlying the second absorber        layer;    -   16. transferring the substrate in a controlled ambient to an        eighth process station; and    -   17. using an eighth physical deposition process in the eighth        process station to cause formation of a second conductor layer.

In a specific embodiment of the method of FIG. 9, the method alsoincludes feed forward control, for example, in-situ monitoringproperties of the layer being formed in each process station anddetermining a process condition in a subsequent physical depositionprocess based on data obtained in the monitoring of the earlierprocesses. In a specific embodiment, the method also includes forming afirst buffer layer overlying the first conductor layer before theformation of the first p-type absorber material. The first buffer layerhas a resistivity greater than about 10 kohm-cm. In another embodiment,a second 1 buffer layer is formed overlying the second n-type windowlayer before the formation of the second conductor layer. The secondbuffer layer is characterized by a resistivity greater than about 10kohm-cm.

FIG. 10 is a simplified flow chart illustrating a method for large scalemanufacture of thin film photovoltaic devices according to anotherembodiment of the present invention. This diagram is merely an example,which should not unduly limit the scope of the claims herein. One ofordinary skill in the art would recognize other variations,modifications, and alternatives. As shown, FIG. 10 illustrates a methodfor manufacturing a tandem cell having three external terminals. Inother words, the top and bottom photovoltaic devices share a commonconductor which is coupled to an external terminal The method can bebriefly summarized below.

-   -   1. loading a substrate into a load lock station, the substrate        including a surface region;    -   2. transferring the substrate in a controlled ambient to a first        process station;    -   3. using a first physical deposition process in the first        process station to cause formation of a first conductor layer        overlying the surface region of the substrate;    -   4. transferring the substrate in a controlled ambient to a        second process station;    -   5. using a second physical deposition process in the second        process station to cause formation of a first p-type absorber        material, the first p-type absorber material comprising at least        a first metal chalcogenide material overlying the first        conductor layer, the first p-type absorber material being        characterized by a first bandgap range and a first thickness        range;    -   6. transferring the substrate in a controlled ambient to a third        process station;    -   7. using a third physical deposition process in the third        process station to cause formation of a first n-type window        layer, the first n-type window layer comprising at least a        second metal chalcogenide material overlying the first p-type        absorber layer;    -   8. transferring the substrate in a controlled ambient to a        fourth process station;    -   9. optionally, using a fourth physical deposition process in the        fourth process station to cause formation of a high resistive        layer;    -   10. transferring the substrate in a controlled ambient to a        fifth process station;    -   11. using a fifth physical deposition process in the fifth        process station to cause formation of a second conductive layer;    -   12. transferring the substrate in a controlled ambient to a        sixth process station;    -   13. using a sixth physical deposition process in the sixth        process station to cause formation of a second p-type absorber        material, the second p-type absorber material comprising at        least a third metal chalcogenide material overlying the        tunneling junction layer, the second p-type absorber material        being characterized by a second bandgap range and a second        thickness range;    -   14. transferring the substrate in a controlled ambient to a        seventh process station;    -   15. using an seventh physical deposition process in the seventh        process station to cause formation of a second n-type window        layer, the second n-type window layer comprising at least a        fourth metal chalcogenide material overlying the second absorber        layer;    -   16. transferring the substrate in a controlled ambient to an        eighth process station; and    -   17. using an eighth physical deposition process in the eighth        process station to cause formation of a third conductor layer.

In a specific embodiment, the method of FIG. 10 also includes feedforward control. That is, the method also includes in-situ monitoringproperties of the layer being formed in each process station anddetermining a process condition in a subsequent physical depositionprocess based on data obtained in the monitoring of the earlierprocesses.

FIG. 11 is a simplified flow chart illustrating a method for large scalemanufacture of thin film photovoltaic devices according to an embodimentof the present invention. This diagram is merely an example, whichshould not unduly limit the scope of the claims herein. One of ordinaryskill in the art would recognize other variations, modifications, andalternatives. As shown, FIG. 11 illustrates a method for large scalemanufacturing of single junction photovoltaic devices including feedforward control. The method can be summarized briefly as follows.

-   -   1. loading a substrate into a load lock station, the substrate        including a surface region;    -   2. transferring the substrate under a controlled ambient to a        first process station;    -   3. using a first physical deposition process in the first        process station to cause formation of a first conductor layer        overlying the surface region of the substrate;    -   4. transferring the substrate under a controlled ambient to a        second process station;    -   5. using a second physical deposition process in the second        process station to cause formation of a first p-type absorber        material, the first p-type absorber material comprising at least        a first metal chalcogenide material overlying the first        conductor layer, the first p-type absorber material being        characterized by a first bandgap range and a first thickness        range;    -   6. monitoring properties of the first p-type absorber material        in the second process station;    -   7. determining a process condition in a third physical        deposition process based on data obtained in the monitoring;    -   8. transferring the substrate in a controlled ambient to a third        process station;    -   9. using the third physical deposition process in the third        process station to cause formation of a first n-type window        layer, the first n-type window layer comprising at least a        second metal chalcogenide material overlying the first p-type        absorber layer,    -   10. transferring the substrate under a controlled ambient to a        fourth process station; and    -   11. using a fourth physical deposition process in the fourth        process station to cause formation of a second conductor layer        overlying the second buffer layer.

FIG. 12 is a simplified flow chart illustrating a method for large scalemanufacture of thin film photovoltaic devices according to anotherembodiment of the present invention. This diagram is merely an example,which should not unduly limit the scope of the claims herein. One ofordinary skill in the art would recognize other variations,modifications, and alternatives. As shown, FIG. 12 illustrates a methodfor making a tandem photovoltaic device having a bottom photovoltaiccell and a top photovoltaic cell using methods similar to those of FIGS.4-11, but also includes in-situ monitoring of the properties of thelower cell. These properties include thin film material properties andelectrical and optical properties of the junction. If the properties arenot within a predetermined specification, then the process and deviceparameters of the upper cell are adjusted. Subsequently the adjustedprocess is used to make the upper cell.

According to another specific embodiment of the present invention, amethod is provided for making a single junction photovoltaic deviceincluding feed forward control. The method can be briefly summarizedbelow.

-   -   1. loading a substrate into a load lock station, the substrate        including a surface region;    -   2. transferring the substrate under a controlled ambient to a        first process station;    -   3. using a first physical deposition process in the first        process station to cause formation of a first conductor layer        overlying the surface region of the substrate;    -   4. transferring the substrate under a controlled ambient to a        second process station;    -   5. using a second physical deposition process in the second        process station to cause formation of a first p-type absorber        material, the first p-type absorber material comprising at least        a first metal chalcogenide material overlying the first        conductor layer, the first p-type absorber material being        characterized by a first bandgap range and a first thickness        range;    -   6. monitoring properties of the first p-type absorber material        in the second process station;    -   7. determining a process condition in a third physical        deposition process based on data obtained in the monitoring;    -   8. transferring the substrate in a controlled ambient to a third        process station;    -   9. using the third physical deposition process in the third        process station to cause formation of a first n-type window        layer, the first n-type window layer comprising at least a        second metal chalcogenide material overlying the first p-type        absorber layer,    -   10. transferring the substrate under a controlled ambient to a        fourth process station; and    -   11. using a fourth physical deposition process in the fourth        process station to cause formation of a second conductor layer        overlying the second buffer layer.

FIG. 13 is a simplified schematic diagram showing a system withsingle-chamber configuration for large scale manufacture of thin filmphotovoltaic cells according to an embodiment of the present invention.This diagram is merely an example, which should not unduly limit thescope of the claims herein. One of ordinary skill in the art wouldrecognize other variations, modifications, and alternatives. As shown, asystem 1300 (at least partially) with single-chamber configuration forlarge scale manufacture of thin film photovoltaic materials is providedand several thin film processes are illustrated. In an embodiment, thesingle-chamber system can be optionally separated into several differentcompartments by a temporary screen 1304 or non-vacuum seal shutter, eventhough each of the different compartments has substantially the samepressure as in the whole chamber. One advantage of having differentcompartments separated in single-chamber configuration is to havecertain degrees of freedom to adjust work gas flow or change the type ofwork gas within individual compartment without interfering processes inother compartment and changing the overall vacuum condition. In aspecific embodiment, certain compartment can still be temporarily vacuumsealed so that it may virtually become a separate chamber versus itsneighboring compartment. For example, FIG. 13 shows that the compartment#4 may be sealed by an removable divider 1306 from other compartment #1,#2, and #3 of the system 1300 with single-chamber configuration.

In an embodiment, a substrate 1310 is provided and loaded (via aload-lock device) on a process stage 1390 in the system 1300 withsingle-chamber configuration. The process stage 1390 is capable offurther transferring, via a plurality of rollers in an example, thesubstrate 1310 along a processing path. For example, the substrate 1310can be moved sequentially from one compartment to another within thechamber for carrying out a large scale batch processing. Of course, FIG.13 just shows an example with merely a schematic diagram of suchtransfer mechanism. In an embodiment, the substrate 1310 is an opticallytransparent solid material. For example, the substrate 1310 can be aglass (e.g., the widely-used soda lime window glass), quartz, fusedsilica, or a plastic, or other composite materials. In an implementationof such system with single-chamber configuration, the substrate 1310 canhave its lateral dimension being compatible with industrial standardsfor making photovoltaic cell. For example, the lateral dimension of thesubstrate 1310 can be about 1 meter. In another example, the lateraldimension of the substrate 1310 can be 1.5 meter or greater. Dependingupon embodiments, the substrate 1310 can be a single material, multiplematerials, which are layered, composites, or stacked, includingcombinations of these, and the like. Of course there can be othervariations, modifications, and alternatives.

As shown in the Compartment #1, the substrate 1310 including a surfaceregion 1311 is held on the process stage exposing to a physical vapordeposition source disposed above the surface region 1311 thereof. Forexample, the deposition source can be a sputtering target 1301 which hassubstantially the same size of the substrate and can be held at adistance above the surface region 1311. In an embodiment, theCompartment #1 is used for growing an electrode layer for a thin filmphotovoltaic cell. In particular, as shown in a small sectional view ofa portion of the substrate 1310, an electrode layer 1320 has beensputter deposited overlying the surface region 1311. In animplementation, the sputtering target 1301 can be made of substantiallymolybdenum material and the Compartment #1 is just part of the systemwith single-chamber configuration that is maintained in a proper vacuumcondition by one or more vacuum pumps (not explicitly shown). Forexample, the chamber pressure can be held at 6.2 mTorr or lower. Withinthe Compartment #1, argon gas with controlled flow rate of about 100sccm can be introduced during the sputtering process. In an alternativeimplementation, pure argon gas plus another gas mixture containing 1%oxygen gas and 99% argon gas with a flow rate of 5-10 sccm can be usedfor forming an ultra thin layer of molybdenum material with tensilestress before covering a thicker layer of molybdenum material withcompressive stress. In those cases, multiple molybdenum targets can bedisposed in the compartment in series along a pathway for transportingthe substrate. Of course, other thin film deposition techniques may beused including evaporation (e.g., using electron beam), chemical vapordeposition, electro-plating, atomic layer deposition, or any combinationof these and the like according to a specific embodiment. The totalthickness of the electrode layer 1320 can be from 300 nm to 400 nm,characterized by resistivity of about 100 ohm-cm to 10 ohm-cm and lessaccording to a specific embodiment for manufacture of a thin filmphotovoltaic cell. In an embodiment, the electrode layer 1320 is made ofmolybdenum material, but can be other material like tungsten, copper,chromium, aluminum, nickel, or platinum. Of course, there can be othervariations, modifications, and alternatives.

Referring to FIG. 13, after the deposition process finishes in theCompartment #1, the substrate 1310 with overlying electrode layer 1320can be transferred from the Compartment #1 to a next compartment,Compartment #2, of the same system 1300 with single-chamberconfiguration. Alternatively, the Compartment #2 and the Compartment #1can be essentially no difference excepting that the processing stage1390 carries the substrate 1310 to a new position for subjecting a nextprocess. At the same time, the process stage 1390 of the system 1300with single-chamber configuration is configured to load a new substrateto the original position associated with the Compartment #1 for formingan electrode layer thereon. Therefore, a continuous processing of largescale manufacture of thin film photovoltaic cells can be carried onwithout breaking the vacuum.

In an embodiment, Compartment #2 is designed for a process of forming acopper-bearing layer overlying the electrode layer on the substrate. Inparticular, performing the process of forming a copper (Cu)-bearinglayer 1330 overlying the electrode layer 1320 can use a sputteringtechnique. At the new position of the process stage 1390 associated withthe Compartment #2, the substrate 1310 with overlying electrode layer1320 is exposed to a Cu bearing sputtering target 1302. In an example, aDC magnetron sputtering technique is used to deposit the Cu-bearinglayer 1330 onto the electrode layer 1320 under following conditions: Thedeposition is controlled to be about a vacuum environment having apressure of 6.2 mTorr or lower with argon gas. The argon gas flow rateis set to about 32 sccm at least within the Compartment #2. Thedeposition can be done with the substrate being held just at roomtemperature. Of course, the Compartment #2 can be configured to provideextra heating to the substrate 1310 or simply absorb certain amount ofplasma heating during the sputtering process. Additionally, theconditions for the sputtering process include a DC power supply of about115 W. According to certain embodiments, DC power in a range from 100 Wto 150 W is suitable depending specific cases with different materials.The full deposition time for the Cu-bearing layer 1330 of about 330 nmthickness is about 6 minutes or more. Of course, the depositioncondition can be varied and modified according to a specific embodiment.For example, a Cu—Ga alloy target may be used to replace the mentionedCu sputtering target so that the formed Cu-bearing layer 1330 comprisesat least copper material and gallium material.

Referring to FIG. 13 again, after the Cu-bearing layer depositionprocess at the Compartment #2, the system 1300 with single-chamberconfiguration is configured to transfer the substrate 1310 withoverlying electrode layer 1320 and Cu-bearing layer 1330 to a nextposition of the same chamber, which may be optionally separated asCompartment #3. In an embodiment, the new position associated with theCompartment #3 is designed to allow the substrate to expose a newdeposition source to continue the processing of manufacture thin filmphotovoltaic cells. For example, at the Compartment #3 an indium (In)layer 1340 as shown can be formed overlying the Cu-bearing layer 1330 onthe substrate 1310. In an implementation of the system 1300 withsingle-chamber configuration, the indium layer 1340 is deposited using asputtering technique by subjecting the Cu-bearing layer 1330 to anIn-based sputtering target 1303 that contains 99.999% pure indium and isseparately disposed from other sputtering targets in differentcompartments. In an implementation, a DC magnetron sputtering techniqueis used to deposit the In layer 1340 under similar conditions but with ashorter deposition time for depositing Cu-bearing layer 1330. Forexample, 2 minutes and 45 seconds may be enough for depositing an Inlayer of about 410 nm in thickness according to a specific embodiment.In another embodiment, the indium layer 1340 can be provided overlyingthe Cu-bearing layer 1330 by an electro-plating process, or othertechniques dependent on specific embodiment.

According to embodiments of the present invention, FIG. 13 illustrate amethod and system with single-chamber configuration of forming amultilayered structure comprising at least copper and indium material ona transparent substrate for manufacture of a thin film photovoltaiccell. In an embodiment, the Cu-bearing layer 1330 as well as the indiumlayer 1340 are provided with a controlled stoichiometric composition sothat the multilayered structure is a Cu-rich copper-indium compositematerial with an atomic ratio of Cu:In greater than 1 therein. Forexample, the atomic ratio of Cu:In within the multilayered structure canbe in a range from 1.2:1 to 2.0:1 or larger depending upon the specificembodiment. In an implementation, the atomic ratio of Cu:In is between1.35:1 and 1.60:1. In another implementation, the atomic ratio of Cu:Inis selected to be about 1.55:1. In a specific embodiment, the formationprocess of indium layer 1340 substantially causes no change in atomicstoichiometry in the Cu-bearing layer 1330 formed earlier.Alternatively, the formation process of the indium layer 1340 can beperformed earlier, at a position associated with the Compartment #2,overlying the electrode layer 1320. While the formation process of theCu-bearing layer 1330 is then performed later, at the positionassociated with the Compartment #3, overlying the indium layer 1340.

Referring further to FIG. 13, the system 1300 with the single-chamberconfiguration includes several compartments for forming a thin filmphotovoltaic cell according to an embodiment of the present invention.As shown, after the formation of the Cu-rich copper-indium compositematerial comprising at least an indium layer 1340 over a Cu-bearinglayer 1330, the substrate 1310 is further transferred to a Compartment#4 to allow the multilayered structure being subjected to a thermaltreatment process. In an example, the Compartment #4 is configured tosupply thermal energy using a plurality of heaters 1305 and provide anenvironment 1307 containing a sulfur bearing species 1308. Theenvironment 1307 may be sealed by an thermally insulated removabledivider 1306 which is closed after transferring the substrate 1310 intothe Compartment #4. The plurality of heaters 1305 are capable of heatingthe Compartment #4 to a temperature of about 400 Degrees Celsius toabout 600 Degrees Celsius for at least about three to fifteen minutes.In a specific embodiment, the plurality of heaters 1305 in the sealedCompartment #4 are configured to become a rapid thermal processor.

In an implementation, the sulfur bearing species 1308 within theenvironment 1307 provided for the Compartment #4 are in a fluid phase.As an example, the sulfur can be provided in a solution, which hasdissolved Na₂S, CS₂, (NH₄)₂S, thiosulfate, and others. In a preferredembodiment, the sulfur bearing species 1308 are hydrogen sulfide gasflowed through a valve into the Compartment #4. In otherimplementations, the sulfur bearing species can be provided in a solidphase and heated or allowed to boil, which vaporizes into a gas phase.In particular, the gas phase sulfur atoms are reacting with the Cu-richcopper-indium composite material within the environment 1307 with atemperature about 500 Degrees Celsius. Other combinations of sulfurbearing species can also be used.

The thermal treatment process performed in the Compartment #4 includescertain predetermined ramp-up and ramp-down periods with certainpredetermined speeds for corresponding temperature changes. For example,the thermal treatment process is a rapid thermal annealing process. Thehydrogen sulfide gas is provided through one or more nozzles with asuitable flow rate control. During the process the Compartment #4 can beconfigured to control the hydrogen sulfide gas pressure using one ormore pumps (not shown). Of course, there can be other variations,modifications, and alternatives.

In an alternative embodiment, the sulfur bearing species can be providedas a layer deposited overlying the Cu-rich copper-indium compositematerial. In a specific embodiment, the sulfur material is provided as aform of coating or a patterned layer. Additionally, the sulfur speciescan be provided as a slurry, powder, solid material, gas, paste, orother suitable forms. Of course, there can be other variations,modifications, and alternatives. Accordingly, the Compartment #4 of thesystem 1300 with single-chamber configuration can be reconfigured toadapt those alternative sulfur incorporation processes.

Referring back to the FIG. 13, the thermal treatment process performedin the Compartment #4 causes a reaction between the Cu-richcopper-indium composite material formed on the substrate 1310 and thegas phase sulfur bearing species 1308 introduced in the Compartment #4.As a result of the reaction, a film with a chalcogenide structure madeof copper indium disulfide material 1360 (or a copper indium galliumdisulfide material if the Cu-bearing composite material includesgallium) can be formed. In one example, the copper indium disulfidematerial 1360 is transformed from the Cu-rich copper-indium compositematerial by incorporating sulfur ions/atoms stripped or decomposed fromthe sulfur bearing species 1308 into the indium layer 1340 overlying theCu-bearing layer 1330 with indium atoms and copper atoms mutuallydiffusing therein. In an embodiment, the thermal treatment process wouldresult in a formation of a cap layer 1370 over the transformed copperindium disulfide material 1360. The cap layer 1370 containssubstantially copper sulfide material but substantially free of indiumatoms. The cap layer 1370 is substantially thinner than the copperindium disulfide material 1360. Depending on the applications, thethickness of the copper sulfide material 1370 is on an order of aboutfive to ten nanometers and greater based on original Cu-richcopper-indium composite material with indium layer 1340 overlyingCu-bearing layer 1330. The cap layer 1370 includes a surface region 1371of the same copper sulfide material substantially free of indium atoms.In a specific embodiment, the formation of this cap layer 1370 isresulted from a diffusive reaction associated with the original Cu-richcopper-indium composite material formed previously. Of course, there canbe other variations, modifications, and alternatives.

FIGS. 14-16 are simplified schematic diagrams illustrating additionalprocesses using the system with multi-chamber configuration formanufacture of a thin film photovoltaic cell according to an embodimentof the present invention. These diagrams are merely examples, whichshould not unduly limit the claims herein. One skilled in the art wouldrecognize other variations, modifications, and alternatives. As shown inFIG. 14, a dip process 1400 is performed to the copper sulfide material1370 that covers the copper indium disulfide thin film 1360. Inparticular, the dip process is an etching process performed by exposingthe surface region 1371 of the copper sulfide material 1370 to 1 toabout 10 wt % solution of potassium cyanide 1410 according to a specificembodiment. The potassium cyanide in solution 1410 acts as an etchantcapable of selectively removing copper sulfide material 1370. Theetching process starts from the exposed surface region 1371 down to thethickness of the copper sulfide material 1370 and substantially stops atthe interface between the copper sulfide material 1370 and copper indiumdisulfide material 1360. As a result the copper sulfide cap layer 1370can be selectively removed by the etching process so that a new surfaceregion 1368 of the remaining copper indium disulfide thin film 1360 isexposed according to a specific embodiment. In a preferred embodiment,the etch selectivity is about 1:100 or more between copper sulfide andcopper indium disulfide. In other embodiments, other selective etchingspecies can be used. In a specific embodiment, the etching species canbe hydrogen peroxide. In other embodiments, other techniques includingelectro-chemical etching, plasma etching, sputter-etching, or anycombination of these can be used. In a specific embodiment, the coppersulfide material can be mechanically removed, chemically removed,electrically removed, or any combination of these, among others. In aspecific embodiment, the absorber layer made of copper indium disulfidematerial or copper indium gallium disulfide material is about 1 to 10microns, but can be others. Of course, there can be other variations,modifications, and alternatives.

The copper indium disulfide material 1360 (or copper indium galliumdisulfide material) formed at previous processes can have a p-typesemiconductor characteristic through a proper impurity doping. Thestructure of the copper indium disulfide material 1360 is a coarsegrained film. Each grain comprises substantially a crystallographicchalcogenide structure, or in general belonging to a chalcopyritestructure, which possesses photoelectric properties with excellentconversion efficiency. In an embodiment, the copper indium disulfidematerial 1360 formed at previous processes can have a p-typesemiconductor characteristic through a proper impurity doping. Inanother embodiment, the copper indium disulfide material 1360 issubjected to additional doping process to form one or more p⁺⁺ regionstherein for the purpose of manufacture of the high efficiency thin filmphotovoltaic cells. In an example, aluminum species are mixed into thecopper indium disulfide material 1360. In another example, the copperindium disulfide material 1360 can be mixed with a copper indiumaluminum disulfide material. Of course, there can be other variations,modifications, and alternatives.

Subsequently as shown in FIG. 15, a window layer 1510 is formedoverlying the p-type copper indium disulfide material 1360. The windowlayer 1510 can be selected from a group of materials consisting of acadmium sulfide (CdS), a zinc sulfide (ZnS), zinc selenium (ZnSe), zincoxide (ZnO), zinc magnesium oxide (ZnMgO), or others and may be dopedwith impurities for conductivity, e.g., n⁺ type. The window layer 1510is intended to serve another part of a PN-junction associated with aphotovoltaic cell. Therefore, the window layer 1510, during or after itsformation, is heavily doped to form a n⁺-type semiconductor layer. Inone example, indium species are used as the doping material to causeformation of the n⁺-type characteristic associated with the window layer1510. In another example, the doping process is performed using suitableconditions. In a specific embodiment, ZnO window layer that is dopedwith aluminum can range from about 200 nm to 500 nm. Of course, therecan be other variations, modifications, and alternative

As shown in FIG. 16, a conductive layer 1530 is added at least partiallyon top of the window layer 1510 to form a top electrode layer for thephotovoltaic device. In one embodiment, the conductive layer 1530 is atransparent conductive oxide TCO layer. For example, TCO can be selectedfrom a group consisting of In₂O₃:Sn (ITO), ZnO:Al (AZO), SnO₂:F (TFO),and can be others. In another embodiment, the formation of the TCO layeris followed a certain predetermined pattern for effectively carried outthe function of top electrode layer for the photovoltaic device withconsiderations of maximizing the efficiency of the thin film basedphotovoltaic devices. In a specific embodiment, the TCO can also act asa window layer, which essentially eliminates a separate window layer. Ofcourse there can be other variations, modifications, and alternatives.

Although the above has been illustrated according to specificembodiments, there can be other modifications, alternatives, andvariations. It is understood that the examples and embodiments describedherein are for illustrative purposes only and that various modificationsor changes in light thereof will be suggested to persons skilled in theart and are to be included within the spirit and purview of thisapplication and scope of the appended claims.

What is claimed is:
 1. A method for manufacture of thin filmphotovoltaic cells in a system with single-chamber configuration havingmultiple compartments therein, the method comprising: providing asubstrate into a first compartment within a chamber, the substrate beingoptically transparent and being characterized by a lateral dimension ofabout 1 meter or greater for manufacture a thin film photovoltaic cell;forming an electrode layer overlying the substrate; transferring thesubstrate within the chamber to a second compartment to subject theelectrode layer to a copper bearing sputtering target; forming acopper-bearing layer overlying the electrode layer; transferring thesubstrate within the chamber to a third compartment to subject thecopper-bearing layer to an indium sputtering target; forming an indiumlayer overlying the copper-bearing layer, thereby forming a Cu-richCu—In composite film having a Cu:In atomic ratio of 1.2:1 and greater;transferring the substrate to a fourth compartment within the chamber,the compartment comprising a plurality of nozzles for supplying gasphase sulfur-bearing species and one or more heaters for supplyingthermal energy; and performing a thermal treatment process to form aphotovoltaic absorber layer by reacting the Cu-rich Cu—In composite filmwith the sulfur-bearing species.
 2. The method of claim 1 wherein thesubstrate comprises a soda lime glass, a quartz, a fused silica, or aplastic, or other composite materials.
 3. The method of claim 1 whereinthe chamber comprises two or more sputtering targets disposed in seriesfor forming the electrode layer characterized by resistivity of about100 ohm-cm to 10 ohm-cm and less.
 4. The method of claim 3 wherein theelectrode layer comprises a conductive material selected frommolybdenum, tungsten, copper, chromium, aluminum, nickel, and platinum.5. The method of claim 3 wherein the electrode layer comprises amolybdenum sublayer with a tensile stress followed by another molybdenumsublayer with a compressive stress.
 6. The method of claim 1 wherein thechamber comprises a vacuum ambient having a pressure of about 6.2 mTorror lower.
 7. The method of claim 1 wherein the copper-bearing layercomprises a pure copper material or a copper-gallium alloy.
 8. Themethod of claim 1 wherein the indium sputtering target is made of99.999% pure indium.
 9. The method of claim 1 wherein the fourthcompartment comprises a rapid thermal annealing processor.
 10. Themethod of claim 1 wherein the one or more heaters are capable of heatingthe compartment from room temperature to about 500 degrees Celsius. 11.The method of claim 1 wherein the gas phase sulfur-bearing speciescomprise a hydrogen sulfide gas, a sulfur vapor from a solid phasesulfide material.
 12. The method of claim 1 wherein the thermal processfurther comprises forming a cap layer made of copper sulfide materialcovering the photovoltaic absorber layer made of copper-indium-disulfidematerial.
 13. The method of claim 12 further comprising performing a dipprocess to remove the copper sulfide cap layer substantially away thecopper-indium-disulfide material.
 14. The method of claim 1 furthercomprising performing a doping process to the photovoltaic absorberlayer using sodium, or boron, or aluminum or any combination of thosematerials as dopant impurities to form one or more p++ regions.
 15. Amethod for manufacture of thin film photovoltaic cells in a system withsingle-chamber configuration having multiple compartments therein, themethod comprising: providing a substrate into a first compartment withinthe chamber, the substrate being optically transparent and beingcharacterized by a lateral dimension of about 1 meter or greater formanufacture a thin film photovoltaic cell; forming an electrode layeroverlying the substrate; transferring the substrate to a secondcompartment within the chamber to subject the electrode layer to acopper bearing sputtering target and an indium bearing sputteringtarget; forming a copper-bearing layer overlying the electrode layer;forming an indium layer overlying the copper-bearing layer, therebyforming a Cu-rich Cu—In composite film having a Cu:In atomic ratio of1.2:1 and greater; transferring the substrate to a third compartmentwithin the chamber, the compartment comprising a plurality of nozzlesfor supplying gas phase sulfur-bearing species and one or more heatersfor supplying thermal energy; and performing a thermal treatment processto form a photovoltaic absorber layer by reacting the Cu-rich Cu—Incomposite film with the sulfur-bearing species.
 16. The method of claim15 wherein the one or more heaters are capable of heating thecompartment from room temperature to about 500 degrees Celsius.
 17. Themethod of claim 15 wherein the gas phase sulfur-bearing species comprisea hydrogen sulfide gas, a sulfur vapor from a solid phase sulfidematerial.
 18. The method of claim 15 wherein the thermal process furthercomprises forming a cap layer made of copper sulfide material coveringthe photovoltaic absorber layer made of copper-indium-disulfidematerial.
 19. The method of claim 18 further comprising performing a dipprocess to remove the copper sulfide cap layer substantially away thecopper-indium-disulfide material.
 20. The method of claim 15, whereinthe transferring the substrate further comprises moving one or moreshutter screens between compartments prior to moving the substrate pastthe opening defined by the movement of the one or more shutter screens.